1. Field of the Invention
The present invention relates to a gas turbine installation for driving a gas turbine for generating electric power, and in particular, to a gas tubine installation adapted to be built in a district in which snowfall can highly be expected.
2. Related Art
In general, there has been known a snow protection method for an intake-air filter in a ventilating and air-conditioning system, in which a snowbreak hood and a louver are mounted to a fresh air inlet of the ventilating and air-conditioning system. In this method, the snowbreak hood can substantially prevent entrance of snow in a normal snowfall condition, and the louver can prevent advance of snow into an intake-air passage by adjusting the opening degree of the louver in such a case that the amount of snowfall is huge or that the advance of snow cannot be fully prevented due to strong wind, in order to prevent the intake filter from clogging with snow.
For example, Japanese Laid-Open Patent No. H8-297188 discloses a snow protection system for a ventilating and air-conditioning system in a nuclear power plant, in which a heating coil is provided downstream of a louver, and a bird net incorporated with a snow-melting heater is provided between the lower end of a snowbreak hood and the lower end of the louver so as to melt snow which has entered since it cannot be melted by the snow melting heater and blocked by the louver, by means of the heating coil in order to prevent the intake-air filter from clogging.
In addition, Japanese Laid-Open Patent No. S61-211647, Japanese Laid-Open No. S61-295448, Japanese Laid-Open Patent No. S61-295449, Japanese Laid-Open Patent No. S62-102044, Japanese Laid-Open Patent No. S62-108939 and Japanese Laid-Open Patent No. H7-209469 also disclose snow protection technology relating ventilation facilities for power plants.
For example, Japanese Laid-Open Patent No. H6-33795 discloses an intake system for a gas turbine, in which bleed air from a low pressure stage of a compressor in the gas turbine is heated along the outer wall surface of the casing of the compressor, and is thereafter injected into the intake-air filter for the gas turbine in order to prevent freezing of the intake-air filter.
Further, Japanese Laid-Open Patent No. H9-317496 discloses an arrangement in which a heat-exchanger is provided in an intake duct of a gas turbine so as to carry out heat-exchange between intake-air into the gas turbine and heating medium in order to heat the intake air in the gas turbine, or to mix the intake-air in the gas turbine with high temperature fluid in order to heat the intake-air into the gas turbine.
Since a predetermined volume of air has to be continuously taken into a gas turbine during operation thereof, the volume of air cannot be reduced by closing a louver even though it is temporary.
Further, gas turbines have such a tendency as the higher the temperature of intake-air, the higher the drive power of a compressor, resulting in lowering of the efficiency of power generation and the output power thereof. In such a method that a heating coil or a heat-exchanger is provided, or high temperature fluid is mixed so as to raise the temperature of a gas turbine in order to melt snow contained in the intake-air, as disclosed in the above-mentioned Japanese Laid-Open Patent No. H8-297188 or Japanese Laid-Open Patent No. H9-317496, there has been offered a problem of lowering the efficiency of power generation and the output power thereof. Further, the operation of a gas turbine requires a large volume of air in comparison with a ventilating and air-conditioning system in a building (for example, a nuclear power plant station), and accordingly, a relatively large heating volume is required for uniformly raising the temperature of this large volume of intake-air required for the operation of the gas turbine, and for sufficiently melting snow contained in the intake-air until the intake-air reaches the inlet of an intake-air filter. Further, should a heating coil or a heat-exchanger is incorporated in an intake-duct, the pressure loss of a gas turbine becomes extremely high, and accordingly, there has been raised a problem of lowering the efficiency of air-intake.
Further, as disclosed in Japanese Laid-Open Patent No. H6-33795, a method in which high temperature air is directly injected into an intake-air filter in order to remove snow stuck to the filter, has offered a problem in heat-resistance, pressure resistance or the like, and further, exhibits a problem of lowering the compression efficiency since bleed air is extracted from a compressor.